Internet Draft Francois Le Faucheur
Editor
Cisco Systems, Inc.
draft-ietf-tsvwg-rsvp-dste-03.txtdraft-ietf-tsvwg-rsvp-dste-04.txt
Aggregation of RSVP Reservations over MPLS TE/DS-TE Tunnels
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Abstract
RFC 3175 specifies aggregation of RSVP end-to-end reservations over
aggregate RSVP reservations. This document specifies aggregation of
RSVP end-to-end reservations over MPLS Traffic Engineering (TE)
tunnels or MPLS Diffserv-aware MPLS Traffic Engineering (DS-TE)
Tunnels. This approach is based on RFC 3175 and simply modifies the
corresponding procedures for operations over MPLS TE tunnels instead
of aggregate RSVP reservations. This approach can be used to achieve
admission control of a very large number of flows in a scalable
manner since the devices in the core of the network are unaware of
the end-to-end RSVP reservations and are only aware of the MPLS TE
tunnels.
Copyright Notice
Copyright (C) The Internet Society (2006).
Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Table of Contents
1. Introduction...................................................2
2. Contributing Authors...........................................6
3. Definitions....................................................7
4. Operations of RSVP Aggregation over TE with pre-established
Tunnels...........................................................8
4.1. Reference Model...........................................9
4.2. Receipt of E2E Path message By the Aggregator............10
4.3. Handling of E2E Path message By Transit LSRs.............11
4.4. Receipt of E2E Path Message by Deaggregator..............11Deaggregator..............12
4.5. Handling of E2E Resv Message by Deaggregator.............12
4.6. Handling of E2E Resv Message by the Aggregator...........13
4.7. Forwarding of E2E traffic by Aggregator..................14
4.8. Removal of E2E reservations..............................14
4.9. Removal of TE Tunnel.....................................15
4.10. Example Signaling Flow..................................16
5. IPv4 and IPv6 Applicability...................................17
6. E2E Reservations Applicability................................17
7. Example Deployment Scenarios..................................17
7.1. Voice and Video Reservations Scenario....................17
7.2. PSTN/3G Voice Trunking Scenario..........................18
8. Optional Use of RSVP Proxy on RSVP Aggregator.................19
9. Security Considerations.......................................21
10.Considerations.......................................19
9. IANA Considerations..........................................22Considerations...........................................20
10. Acknowledgments..............................................20
11. Acknowledgments..............................................22
12. Normative References.........................................22
13.References.........................................20
12. Informative References.......................................23
14.References.......................................21
13. Editor's Address:............................................24Address:............................................22
Appendix A - Optional Use of RSVP Proxy on RSVP Aggregator.......23
Appendix B - Example Usage of RSVP Aggregation over DSTE Tunnels for
VoIP Call Admission Control (CAC)................................25
1. Introduction
The Integrated Services (Intserv) [INT-SERV] architecture provides a
means for the delivery of end-to-end Quality of Service (QoS) to
applications over heterogeneous networks.
[RSVP] defines the Resource reSerVation Protocol which can be used by
applications to request resources from the network. The network
responds by explicitely admitting or rejecting these RSVP requests.
Certain applications that have quantifiable resource requirements
express these requirements using Intserv parameters as defined in the
appropriate Intserv service specifications ([GUARANTEED],
[CONTROLLED]).
The Differentiated Services (DiffServ) architecture ([DIFFSERV]) was
then developed to support differentiated treatment of packets in very
large scale environments. In contrast to the per-flow orientation of
Intserv and RSVP, Diffserv networks classify packets into one of a
small number of aggregated flows or "classes", based on the Diffserv
codepoint (DSCP) in the packet IP header. At each Diffserv router,
packets are subjected to a "per-hop behavior" (PHB), which is invoked
by the DSCP. The primary benefit of Diffserv is its scalability.
Diffserv eliminates the need for per-flow state and per-flow
processing and therefore scales well to large networks.
However, DiffServ does not include any mechanism for communication
between applications and the network. Thus, as detailed in [INT-DIFF],
significant benefits can be achieved by using Intserv over Diffserv
including resource based admission control, policy based admission
control, assistance in traffic identification /classification and
traffic conditioning. As discussed in [INT-DIFF], Intserv can operate
over Diffserv in multiple ways. For example, the Diffserv region may
be statically provisioned or may be RSVP aware. When it is RSVP aware,
several mechanisms may be used to support dynamic provisioning and
topology aware admission control including aggregate RSVP
reservations, per flow RSVP or a bandwidth broker. The advantage of
using aggregate RSVP reservations is that it offers dynamic,
topology-aware admission control over the Diffserv region without
per-flow reservations and the associated level of RSVP signaling in
the Diffserv core. In turn, this allows dynamic, topology aware
admission control of flows requiring QoS reservations over the
Diffserv core even when the total number of such flows carried over
the Diffserv core is extremely large.
[RSVP-AGG] describes in detail how to perform such aggregation of end
to end RSVP reservations over aggregate RSVP reservations in a
Diffserv cloud. It establishes an architecture where multiple end-to-
end RSVP reservations sharing the same ingress router (Aggregator)
and the same egress router (Deaggregator) at the edges of an
"aggregation region", can be mapped onto a single aggregate
reservation within the aggregation region. This considerably reduces
the amount of reservation state that needs to be maintained by
routers within the aggregation region. Furthermore, traffic belonging
to aggregate reservations is classified in the data path purely using
Diffserv marking.
[MPLS-TE] describes how MPLS Traffic Engineering (TE) Tunnels can be
used to carry arbitrary aggregates of traffic for the purposes of
traffic engineering. [RSVP-TE] specifies how such MPLS TE Tunnels can
be established using RSVP-TE signaling. MPLS TE uses Constraint Based
Routing to compute the path for a TE tunnel. Then, Admission Control
is performed during the establishment of TE Tunnels to ensure they
are granted their requested resources.
[DSTE-REQ] presents the Service Providers requirements for support of
Diff-Serv-aware MPLS Traffic Engineering (DS-TE). With DS-TE,
separate DS-TE tunnels can be used to carry different Diffserv
classes of traffic and different resource constraints can be enforced
for these different classes. [DSTE-PROTO] specifies RSVP-TE signaling
extensions as well as OSPF and ISIS extensions for support of DS-TE.
In the rest of this document we will refer to both TE tunnels and DS-
TE tunnels simply as "TE tunnels".
TE tunnels have much in common with the aggregate RSVP reservations
used in [RSVP-AGG]:
- a TE tunnel is subject to Admission Control and thus is
effectively an aggregate bandwidth reservation
- In the data plane, packet scheduling relies exclusively on
Diff-Serv classification and PHBs
- Both TE tunnels and aggregate RSVP reservations are controlled
by "intelligent" devices on the edge of the "aggregation core"
(Head-end and Tail-end in the case of TE tunnels, Aggregator
and Deaggregator in the case of aggregate RSVP reservations
- Both TE tunnels and aggregate RSVP reservations are signaled
using the RSVP protocol (with some extensions defined in [RSVP-
TE] and [DSTE-PROTO] respectively for TE tunnels and DS-TE
tunnels).
This document provides a detailed specification for performing
aggregation of end-to-end RSVP reservations over MPLS TE tunnels
(which act as aggregate reservations in the core). This document
builds on the RSVP Aggregation procedures defined in [RSVP-AGG], and
only changes those where necessary to operate over TE tunnels. With
[RSVP-AGG], a lot of responsibilities (such as mapping end-to-end
reservations to Aggregate reservations and resizing the Aggregate
reservations) are assigned to the Deaggregator (which is the
equivalent of the Tunnel Tail-end) while with TE, the tunnels are
controlled by the Tunnel Head-end. Hence, the main change over the
RSVP Aggregations procedures defined in [RSVP-AGG] is to modify these
procedures to reassign responsibilities from the Deaggregator to the
Aggregator (i.e. the tunnel Head-end).
[LSP-HIER] defines how to aggregate MPLS TE Label Switched Paths
(LSPs) by creating a hierarchy of such LSPs. This involves nesting of
end-to-end LSPs into an aggregate LSP in the core (by using the label
stack construct). Since end-to-end TE LSPs are themselves signaled
with RSVP-TE and reserve resources at every hop, this can be looked
at as a form of aggregation of RSVP(-TE) reservations over MPLS TE
Tunnels. This document capitalizes on the similarities between
nesting of TE LSPs over TE tunnels and RSVP aggregation over TE
tunnels and reuses the procedures of [LSP-HIER] wherever possible.
This document also builds on the "RSVP over Tunnels" concepts of RFC
2746 [RSVP-TUN]. It differs from that specification in the following
ways
- Whereas RFC 2746 describes operation with IP tunnels, this
document describes operation over MPLS tunnels. One consequence
of this difference is the need to deal with penultimate hop
popping (PHP).
- MPLS-TE tunnels inherently reserve resources, whereas the
tunnels in RFC 2746 do not have resource reservations by
default. This leads to some simplifications in the current
document.
- ThereThis document builds on the fact that there is exactly one
aggregate reservation per MPLS-TE tunnel, whereas RFC 2746
permits many reservations per tunnel.a model where one reservation is established on the
tunnel path for each end-to-end flow.
- We have assumed in the current document that a given MPLS-TE
tunnel will carry reserved traffic and nothing but reserved
traffic, which negates the requirement of RFC 2746 to
distinguish reserved and non-reserved traffic traversing the
same tunnel by using distinct encapsulations.
- There may be several MPLS-TE tunnels that share common head and
tail end routers, with head-end policy determining which tunnel
is appropriate for a particular flow. This scenario does not
appear to be addressed in RFC 2746.
At the same time, this document does have many similarities with RFC
2746. MPLS-TE tunnels are "type 2 tunnels" in the nomenclature of RFC
2746:
"
The (logical) link may be able to promise that some overall
level of resources is available to carry traffic, but not to
allocate resources specifically to individual data flows.
"
Aggregation of end-to-end RSVP reservations over TE tunnels combines
the benefits of [RSVP-AGG] with the benefits of MPLS including the
following:
- applications can benefit from dynamic, topology-aware resource-
based admission control over any segment of the end to end path
including the core
- as per regular RSVP behavior, RSVP does not impose any burden
on routers where such admission control is not needed (for
example if the links upstream and downstream of the MPLS TE
core are vastly over-engineered compared to the core capacity,
admission control is not required on these over-engineered
links and RSVP need not be processed on the corresponding
router hops)
- the core scalability is not affected (relative to the
traditional MPLS TE deployment model) since the core remains
unaware of end-to-end RSVP reservations and only has to
maintain aggregate TE tunnels and since the datapath
classification and scheduling in the core relies purely on
Diffserv mechanism (or more precisely MPLS Diffserv mechanisms
as specified in [DIFF-MPLS])
- the aggregate reservation (and thus the traffic from the
corresponding end to end reservations) can be network
engineered via the use of Constraint based routing (e.g.
affinity, optimization on different metrics) and when needed
can take advantage of resources on other paths than the
shortest path
- the aggregate reservations (and thus the traffic from the
corresponding end to end reservations) can be protected against
failure through the use of MPLS Fast Reroute
This document, like [RSVP-AGG], covers aggregation of unicast
sessions. Aggregation of multicast sessions is for further study.
2. Contributing Authors
This document was the collective work of several authors. The text
and content were contributed by the editor and the co-authors listed
below. (The contact information for the editor appears in the
Editor's Address section.)
Michael DiBiasio
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, MA 01719
USA
Email: dibiasio@cisco.com
Bruce Davie
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, MA 01719
USA
Email: bdavie@cisco.com
Christou Christou
Booz Allen Hamilton
8283 Greensboro Drive
McLean, VA 22102
USA
Email: christou_chris@bah.com
Michael Davenport
Booz Allen Hamilton
8283 Greensboro Drive
McLean, VA 22102
USA
Email: davenport_michael@bah.com
Jerry Ash
AT&T
200 Laurel Avenue
Middletown, NJ 07748, USA
USA
Email: gash@att.com
Bur Goode
AT&T
32 Old Orchard Drive
Weston, CT 06883
USA
Email: bgoode@att.com
3. Definitions
For readability, a number of definitions from [RSVP-AGG] as well as
definitions for commonly used MPLS TE terms are provided here:
Aggregator This is the process in (or associated with) the router
at the ingress edge of the aggregation region (with
respect to the end to end RSVP reservation) and
behaving in accordance with [RSVP-AGG]. In this
document, it is also the TE Tunnel Head-end.
Deaggregator This is the process in (or associated with) the router
at the egress edge of the aggregation region (with
respect to the end to end RSVP reservation) and
behaving in accordance with [RSVP-AGG]. In this
document, it is also the TE Tunnel Tail-end
E2E End to end
E2E reservation This is an RSVP reservation such that:
(i) corresponding Path messages are initiated
upstream of the Aggregator and terminated
downstream of the Deaggregator, and
(ii) corresponding Resv messages are initiated
downstream of the Deaggregator and
terminated upstream of the Aggregator, and
(iii) this RSVP reservation is to be aggregated
over an MPLS TE tunnel between the
Aggregator and Deaggregator.
An E2E RSVP reservation may be a per-flow
reservation. Alternatively, the E2E reservation
may itself be an aggregate reservation of various
types (e.g. Aggregate IP reservation, Aggregate
IPsec reservation). See section 5 and 6 for more
details on the types of E2E RSVP reservations. As
per regular RSVP operations, E2E RSVP reservations
are unidirectional.
Head-end
This is the Label Switch Router responsible for
establishing, maintaining and tearing down a given TE
tunnel.
Tail-end
This is the Label Switch Router responsible for
terminating a given TE tunnel
Transit LSR This is a Label Switch router that is on the path of a
given TE tunnel and is neither the Head-end nor the
Tail-end
4. Operations of RSVP Aggregation over TE with pre-established Tunnels
[RSVP-AGG] supports operations both in the case where aggregate RSVP
reservations are pre-established and in the case where Aggregators
and Deaggregators have to dynamically discover each other and
dynamically establish the necessary aggregate RSVP reservations.
Similarly, RSVP Aggregation over TE tunnels could operate both in the
case where the TE tunnels are pre-established and in the case where
the tunnels need to be dynamically established.
In this document we provide a detailed description of the procedures
in the case where TE tunnels are already established. These
procedures are based on those defined in [LSP-HIER]. The routing
aspects discussed in section 3 of [LSP-HIER] are not relevant here
because those aim at allowing the constraint based routing of end-to-
end TE LSPs to take into account the (aggregate) TE tunnels. In the
present document, the end-to-end RSVP reservations to be aggregated
over the TE tunnels rely on regular SPF routing. However, as already
mentioned in [LSP-HIER], we note that a TE Tunnel may be advertised
into ISIS or OSPF, to be used in normal SPF by nodes upstream of the
Aggregator. This would affect SPF routing and thus routing of end-to-
end RSVP reservations. The control of aggregation boundaries
discussed in section 6 of [LSP-HIER] is also not relevant here. This
uses information exchanged in GMPLS protocols to dynamically discover
the aggregation boundary. In this document, TE tunnels are pre-
established, so that the aggregation boundary can be easily inferred.
The signaling aspects discussed in section 6.2 of [LSP-HIER] apply to
the establishment/termination of the aggregate TE tunnels when this
is triggered by GMPLS mechanisms (e.g. as a result of an end-to-end
TE LSP establishment request received at the aggregation boundary) .
As this document assumes pre-established tunnels, those aspects are
not relevant here. The signaling aspects discussed in section 6.1 of
[LSP-HIER] relate to the establishment/maintenance of the end-to-end
TE LSPs over the aggregate TE tunnel. This document describes how to
use the same procedures as those specified in section 6.1 of [LSP-
HIER], but for the establishment of end-to-end RSVP reservations
(instead of end-to-end TE LSPs) over the TE tunnels. This is covered
further in section 4 of the present document.
Pre-establishment of the TE tunnels may be triggered by any
mechanisms including for example manual configuration or automatic
establishment of a TE tunnel mesh through dynamic discovery of TE
Mesh membership as allowed in [AUTOMESH].
Procedures in the case of dynamically established TE tunnels are for
further studies.
4.1. Reference Model
I----I I----I
H--I R I\ I-----I I------I /I R I--H
H--I I\\I I I---I I I//I I--H
I----I \I He/ I I T I I Te/ I/ I----I
I Agg I=======================I Deag I
/I I I I I I\
H--------//I I I---I I I\\--------H
H--------/ I-----I I------I \--------H
H = Host requesting end-to-end RSVP reservations
R = RSVP router
He/Agg = TE tunnel Head-end/Aggregator
Te/Deag = TE tunnel Tail-end/Deaggregator
T = Transit LSR
-- = E2E RSVP reservation
== = TE Tunnel
4.2. Receipt of E2E Path message By the Aggregator
The first event is the arrival of the E2E Path message at the
Aggregator. The Aggregator MUST follow traditional RSVP procedures
for processing of this E2E path message augmented with the extensions
documented in this section.
The Aggregator MUST first attempt to map the E2E reservation onto a
TE tunnel. This decision is made in accordance with routing
information as well as any local policy information that may be
available at the Aggregator. Examples of such policies appear in the
following paragraphs. Just for illustration purposes, among many
other criteria, such mapping policies might take into account the
Intserv service type, the Application Identity [RSVP-APPID] and/or
the signaled preemption [RSVP-PREEMP] of the E2E reservation (for
example, the aggregator may take into account the E2E reservations
RSVP preemption priority and the MPLS TE Tunnel set-up and/or hold
priorities when mapping the E2E reservation onto an MPLS TE tunnel).
There are situations where the Aggregator is able to make a final
mapping decision. That would be the case, for example, if there is a
single TE tunnel towards the destination and if the policy is to map
any E2E RSVP reservation onto TE Tunnels.
There are situations where the Aggregator is not able to make a final
determination. That would be the case, for example, if routing
identifies two DS-TE tunnels towards the destination, one belonging
to DS-TE Class-Type 1 and one to Class-Type 0, if the policy is to
map Intserv Guaranteed Services reservations to a Class-Type 1 tunnel
and Intserv Controlled Load reservations to a Class-Type 0 tunnel,
and if the E2E RSVP Path message advertises both Guaranteed Service
and Controlled Load.
Whether final or tentative, the Aggregator makes a mapping decision
and selects a TE tunnel. Before forwarding the E2E Path message
towards the receiver, the Aggregator SHOULD update the ADSPEC inside
the E2E Path message to reflect the impact of the MPLS TE cloud onto
the QoS achievable by the E2E flow. This update is a local matter and
may be based on configured information, on information available in
the MPLS TE topology database, on the current TE tunnel path, on
information collected via RSVP-TE signaling, or combinations of those.
Updating the ADSPEC allow receivers that take into account the
information collected in the ADSPEC within the network (such as delay
and bandwidth estimates) to make more informed reservation decisions.
The Aggregator MUST then forward the E2E Path message to the
Deaggregator (which is the tail-end of the selected TE tunnel). In
accordance with [LSP-HIER], the Aggregator MUST send the E2E Path
message with an IF_ID RSVP_HOP object instead of an RSVP_HOP object.
The data interface identification MUST identify the TE Tunnel.
To send the E2E Path message, the Aggregator MUST address it directly
to the Deaggregator by setting the destination address in the IP
Header of the E2E Path message to the Deaggregator address. The
Router Alert is not set in the E2E Path message.
Optionally, the Aggregator MAY also encapsulate the E2E Path message
in an IP tunnel or in the TE tunnel itself.
Regardless of the encapsulation method, the Router Alert is not set.
Thus, the E2E Path message will not be visible to routers along the
path from the Aggregator to the Deaggregator. Therefore, in contrast
to the procedures of [RSVP-AGG], the IP Protocol number need not be
modified to "RSVP-E2E-IGNORE"; it MUST be left as is (indicating
"RSVP") by the Aggregator.
In some environments, the Aggregator and Deaggregator MAY also act as
IPsec Security Gateways in order to provide IPsec protection to E2E
traffic when it transits between the Aggregator and the Deaggregator.
In that case, to transmit the E2E Path message to the Deaggregator,
the Aggregator MUST send the E2E Path message into the relevant IPsec
tunnel terminating on the Deaggregator.
E2E PathTear and ResvConf messages MUST be forwarded by the
Aggregator to the Deaggregator exactly like Path messages.
4.3. Handling of E2E Path message By Transit LSRs
Since the E2E Path message is addressed directly to the Deaggregator
and does not have Router Alert set, it is hidden from all transit
LSRs.
4.4. Receipt of E2E Path Message by Deaggregator
On receipt of the E2E Path message addressed to it, the Deaggregator
will notice that the IP Protocol number is set to "RSVP" and will
thus perform RSVP processing of the E2E Path message.
As with [LSP-HIER], the IP TTL vs. RSVP TTL check MUST NOT be made.
The Deaggregator is informed that this check is not to be made
because of the presence of the IF_ID RSVP HOP object.
The Deaggregator MAY support the option to perform the following
checks (defined in [LSP-HIER]) by the receiver Y of the IF_ID
RSVP_HOP object:
1. Make sure that the data interface identified in the IF_ID
RSVP_HOP object actually terminates on Y.
2. Find the "other end" of the above data interface, say X.
Make sure that the PHOP in the IF_ID RSVP_HOP object is a
control channel address that belongs to the same node as X.
The information necessary to perform these checks may not always be
available to the Deaggregator. Hence, the Deaggregator MUST support
operations in such environments where the checks cannot be made.
The Deaggregator MUST forward the E2E Path downstream towards the
receiver. In doing so, the Deaggregator sets the destination address
in the IP header of the E2E Path message to the IP address found in
the destination address field of the Session object. The Deaggregator
also sets the Router Alert.
An E2E PathErr sent by the Deaggregator in response to the E2E Path
message (which contains an IF_ID RSVP_HOP object) SHOULD contain an
IF_ID RSVP_HOP object.
4.5. Handling of E2E Resv Message by Deaggregator
As per regular RSVP operations, after receipt of the E2E Path, the
receiver generates an E2E Resv message which travels upstream hop-by-
hop towards the sender.
On receipt of the E2E Resv, the Deaggregator MUST follow traditional
RSVP procedures on receipt of the E2E Resv message. This includes
performing admission control for the segment downstream of the
Deaggregator and forwarding the E2E Resv message to the PHOP signaled
earlier in the E2E Path message and which identifies the Aggregator.
Since the E2E Resv message is directly addressed to the Aggregator
and does not carry the Router Alert option (as per traditional RSVP
Resv procedures), the E2E Resv message is hidden from the routers
between the Deaggregator and the Aggregator which, therefore, handle
the E2E Resv message as a regular IP packet.
If the Aggregator and Deaggregator are also acting as IPsec Security
Gateways, the Deaggregator MUST send the E2E Resv message into the
relevant IPsec tunnel terminating on the Aggregator.
4.6. Handling of E2E Resv Message by the Aggregator
The Aggregator is responsible for ensuring that there is sufficient
bandwidth available and reserved over the appropriate TE tunnel to
the Deaggregator for the E2E reservation.
On receipt of the E2E Resv message, the Aggregator MUST first perform
the final mapping onto the final TE tunnel (if the previous mapping
was only a tentative one).
If the tunnel did not change during the final mapping, the Aggregator
continues processing of the E2E Resv as described in the four
following paragraphs.
The aggregator calculates the size of the resource request using
traditional RSVP procedures. That is, it follows the procedures in
[RSVP] to determine the resource requirements from the Sender Tspec
and the Flowspec contained in the Resv. Then it compares the resource
request with the available resources of the selected TE tunnel.
If sufficient bandwidth is available on the final TE tunnel, the
Aggregator MUST update its internal understanding of how much of the
TE Tunnel is in use and MUST forward the E2E Resv messages to the
corresponding PHOP.
As noted in [RSVP-AGG], a range of policies MAY be applied to the re-
sizing of the aggregate reservation (in this case, the TE tunnel.)
For example, the policy may be that the reserved bandwidth of the
tunnel can only be changed by configuration. More dynamic policies
are also possible, whereby the aggregator may attempt to increase the
reserved bandwidth of the tunnel in response to the amount of
allocated bandwidth that has been used by E2E reservations.
Furthermore, to avoid the delay associated with the increase of the
Tunnel size, the Aggregator may attempt to anticipate the increases
in demand and adjust the TE tunnel size ahead of actual needs by E2E
reservations. In order to reduce disruptions, the aggregator SHOULD
use "make-before-break" procedures as described in [RSVP-TE] to alter
the TE tunnel bandwidth".
If sufficient bandwidth is not available on the final TE Tunnel, the
Aggregator MUST follow the normal RSVP procedure for a reservation
being placed with insufficient bandwidth to support this reservation.
That is, the reservation is not installed and a ResvError is sent
back towards the receiver.
If the tunnel did change during the final mapping, the Aggregator
MUST first resend to the Deaggregator an E2E Path message with the
IF_ID RSVP_HOP data interface identification identifying the final TE
Tunnel. If needed, the ADSPEC information in this E2E Path message
SHOULD be updated. Then the Aggregator MUST
- either drop the E2E Resv message
- or proceed with the processing of the E2E Resv in the same
manner as in the case where the tunnel did not change and
described above.
In the former case, admission control over the final TE tunnel (and
forwarding of E2E Resv message upstream towards the sender) would
only occur when the Aggregator receives the subsequent E2E Resv
message (that will be sent by the Deaggregator in response to the
resent E2E Path). In the latter case, admission control over the
final Tunnel is carried out by Aggregator right away and if
successful the E2E Resv message is generated upstream towards the
sender.
On receipt of an E2E ResvConf from the Aggregator, the Deaggregator
MUST forward the E2E ResvConf downstream towards the receiver. In
doing so, the Deaggregator sets the destination address in the IP
header of the E2E ResvConf message to the IP address found in the
RESV_CONFIRM object of the corresponding Resv. The Deaggregator also
sets the Router Alert.
4.7. Forwarding of E2E traffic by Aggregator
When the Aggregator receives a data packet belonging to an E2E
reservations currently mapped over a given TE tunnel, the Aggregator
MUST encapsulate the packet into that TE tunnel.
If the Aggregator and Deaggregator are also acting as IPsec Security
Gateways, the Aggregator MUST also encapsulate the data packet into
the relevant IPsec tunnel terminating on the Deaggregator before
transmission into the MPLS TE tunnel.
4.8. Removal of E2E reservations
E2E reservations are removed in the usual way via PathTear, ResvTear,
timeout, or as the result of an error condition. When a reservation
is removed, the Aggregator MUST update its local view of the
resources available on the corresponding TE tunnel accordingly.
4.9. Removal of TE Tunnel
Should a TE Tunnel go away (presumably due to a configuration change,
route change, or policy event), the aggregator behaves much like a
conventional RSVP router in the face of a link failure. That is, it
may try to forward the Path messages onto another tunnel, if routing
and policy permit, or it may send Path_Error messages to the sender
if no suitable tunnel exists. In case the Path messages are forwarded
onto another tunnel which terminates on a different Deaggregator, or
the reservation is torn-down via Path Error messages, the reservation
state established on the router acting as the Deaggregator before the
TE tunnel went away, will time out since it will no longer be
refreshed.
4.10. Example Signaling Flow
Aggregator Deaggregator
(*)
RSVP-TE Path
=========================>
RSVP-TE Resv
<=========================
(**)
E2E Path
-------------->
(1)
E2E Path
------------------------------->
(2)
E2E Path
----------->
E2E Resv
<-----------
(3)
E2E Resv
<-----------------------------
(4)
E2E Resv
<-------------
(*) Aggregator is triggered to pre-establish the TE Tunnel(s)
(**) TE Tunnel(s) are pre-established
(1) Aggregator tentatively selects the TE tunnel and forwards
E2E path to Deaggregator
(2) Deaggregator forwards the E2E Path towards receiver
(3) Deaggregator forwards the E2E Resv to the Aggregator
(4) Aggregator selects final TE tunnel, checks that there is
sufficient bandwidth on TE tunnel and forwards E2E Resv to
PHOP. If final tunnel is different from tunnel tentatively
selected, the Aggregator re-sends an E2E Path.
5. IPv4 and IPv6 Applicability
The procedures defined in this document are applicable to all the
following cases:
(1) Aggregation of E2E IPv4 RSVP reservations over IPv4 TE
Tunnels
(2) Aggregation of E2E IPv6 RSVP reservations over IPv6 TE
Tunnels
(3) Aggregation of E2E IPv6 RSVP reservations over IPv4 TE
tunnels, provided a mechanism such as [6PE] is used by the
Aggregator and Deaggregator for routing of IPv6 traffic over
an IPv4 MPLS core,
(4) Aggregation of E2E IPv4 RSVP reservations over IPv6 TE
tunnels, provided a mechanism is used by the Aggregator and
Deaggregator for routing IPv4 traffic over IPv6 MPLS.
6. E2E Reservations Applicability
The procedures defined in this document are applicable to many types
of E2E RSVP reservations including the following cases:
(1) the E2E RSVP reservation is a per-flow reservation where the
flow is characterized by the usual 5-tuple
(2) the E2E reservation is an aggregate reservation for multiple
flows as described in [RSVP-AGG] or [RSVP-GEN-AGG] where the
set of flows is characterized by the <source address,
destination address, DSCP>
(3) the E2E reservation is a reservation for an IPsec protected
flow. For example, where the flow is characterized by the
<source address, destination address, SPI> as described in
[RSVP-IPSEC].
7. Example Deployment Scenarios
7.1. Voice and Video Reservations Scenario
An example application of the procedures specified in this document
is admission control of voice and video in environments with very
high numbers of hosts. In the example illustrated below, hosts
generate end-to-end per-flow reservations for each of their video
streams associated with a video-conference, each of their audio
streams associated with a video-conference and each of their voice
calls. These reservations are aggregated over MPLS DS-TE tunnels over
the packet core. The mapping policy defined by the user maybe that
all the reservations for audio and voice streams are mapped onto DS-
TE tunnels of Class-Type 1 while reservations for video streams are
mapped onto DS-TE tunnels of Class-Type 0.
------ ------
I H I# ------- -------- #I H I
I I\#I I ----- I I#/I I
-----I \I Agg I I T I I Deag I/ ------
I I==========================I I
------ /I I::::::::::I I:::::::::::I I\ ------
I H I/#I I ----- I I#\I H I
I I# ------- -------- #I I
------ ------
H = Host
Agg = Aggregator (TE Tunnel Head-end)
Deagg = Deaggregator (TE Tunnel Tail-end)
T = Transit LSR
/ = E2E RSVP reservation for a Voice flow
# = E2E RSVP reservation for a Video flow
== = DS-TE Tunnel from Class-Type 1
:: = DS-TE Tunnel from Class-Type 0
7.2. PSTN/3G Voice Trunking Scenario
An example application of the procedures specified in this document
is voice call admission control in large scale telephony trunking
environments. A Trunk VoIP Gateway may generate one aggregate RSVP
reservation for all the calls in place towards another given remote
Trunk VoIP Gateway (with resizing of this aggregate reservation in a
step function depending on current number of calls). In turn, these
reservations may be aggregated over MPLS TE tunnels over the packet
core so that tunnel Head-ends act as Aggregators and perform
admission control of Trunk Gateway reservations into MPLS TE Tunnels.
The MPLS TE tunnels may be protected by MPLS Fast Reroute.
This scenario is illustrated below:
------ ------
I GW I\ ------- -------- /I GW I
I I\\I I ----- I I//I I
-----I \I Agg I I T I I Deag I/ ------
I I==========================I I
------ /I I I I I I\ ------
I GW I//I I ----- I I\\I GW I
I I/ ------- -------- \I I
------ ------
GW = VoIP Gateway
Agg = Aggregator (TE Tunnel Head-end)
Deagg = Deaggregator (TE Tunnel Tail-end)
T = Transit LSR
/ = Aggregate Gateway to Gateway E2E RSVP reservation
== = TE Tunnel
8. Optional UseSecurity Considerations
The security issues inherent to the use of RSVP, RSVP Proxy on RSVP Aggregator
A number of approaches ([RSVP-PROXY], [L-RSVP]) have been, or are
being,Aggregation and
MPLS TE apply. Those can be addressed as discussed in [RSVP], [RSVP-
AGG] and [RSVP-TE].
Section 7 of [LSP-HIER] discusses security considerations stemming
from the IETF in order to allow a network node to
behave as an RSVP proxy which:
- originates the Resv Message (in response tofact that the Path message) on
behalfimplicit assumption of a binding between data
interface and the destination node
- originates the Pathinterface over which a control message (in responseis sent is
no longer valid. These security considerations are equally applicable
to some trigger) on
behalf of the source node.
We observe that such approaches may optionally be used in conjunction
with the aggregation of RSVP reservations over MPLS TE tunnels as
specified in thispresent document.
In particular, we consideraddition, in the case where the RSVP Aggregator/Deaggregator also behaves asAggregators dynamically resize the
TE tunnels based on the current level of reservation, there are risks
that the TE tunnels used for RSVP proxy.
As discussed in [RSVP-PROXY]:
"The proxy functionality does not imply merely generating a single
Resv message. Proxying the Resv involves installing stateaggregation hog resources in the node
doing the proxy i.e. the proxying node should act as if it had
received a Resvcore which could prevent other TE Tunnels from the true endpoint. This involves reserving
resources (if required), sending periodic refreshes of the Resv
messagebeing established.
There are also potential risks that such resizing results in
significant computation and tearing down the reservation if the Path is torn down."
Hence, when behavingsignaling as the RSVP Proxy, the RSVP Aggregator may
effectively perform resource reservation over the MPLSwell as churn on tunnel
paths. Such risks can be mitigated by configuration options allowing
control of TE Tunnel (and
hence overtunnel dynamic resizing (maximum Te tunnel size,
maximum resizing frequency,...) and/or possibly by the whole segment betweenuse of TE
preemption.
If the RSVP Aggregator and Deaggregator are also acting as IPsec Security
Gateways, the RSVP
Deaggregator) even if the RSVP signaling only takes place upstreamSecurity Considerations of [SEC-ARCH] apply.
9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgments
This document builds on the MPLS TE Tunnel (i.e. between the host[RSVP-AGG], [RSVP-TUN] and the RSVP aggregator).[LSP-HIER]
specifications. Also, the RSVP Proxy can generate the Path message on behalf of the
remote source host in order to achieve reservation in the return
direction (i.e. from RSVP aggregator/Deaggregatorwe would like to host).
The resulting Signaling Flow is illustrated below, covering
reservations for both directions:
I----I I--------------I I------I I--------------I I----I
I I I Aggregator/ I I MPLS I I Aggregator/ I I I
IHostI I Deaggregator/I I cloudI I Deaggregator/I IHostI
I I I RSVP Proxy I I I I RSVP Proxy I I I
I----I I--------------I I------I I--------------I I----I
==========TE Tunnel==========>
<========= TE Tunnel==========
Path Path
------------> (1)-\ /-(i) <----------
Resv I I Resv
<------------ (2)-/ \-(ii) ------------>
Path Path
<------------ (3) (iii) ------------>
Resv Resv
------------> <------------
(1)(i) : Aggregator/Deaggregator/Proxy receives Path message,
selects the TE tunnel, performs admission control over the TE Tunnel.
(1) and (i) happens independently of each other.
(2)(ii) : Aggregator/Deaggregator/Proxy generates the Resv message
towards Host. (2) is triggered by (1)thank Tom Phelan, John Drake,
Arthi Ayyangar, Fred Baker, Subha Dhesikan, Kwok-Ho Chan, Carol
Iturralde and (ii) is triggered by (i).
Before generatingJames Gibson for their input into this Resv message, the Aggregator/Proxy performs
admission control of the corresponding reservation over the TE tunnel
that will eventually carry the corresponding traffic.
(3)(iii) : Aggregator/Deaggregator/Proxy generates the Path message
towards Hostdocument.
11. Normative References
[RFC2119] S. Bradner, Key words for reservationuse in return direction. The actual trigger
for this depends on the actual RSVP proxy solution. As an example,
(3) and (iii) may simply be triggered respectively by (1)RFCs to Indicate
Requirement Levels, RFC2119, March 1997.
[RFC3668] S. Bradner, Intellectual Property Rights in IETF Technology,
RFC 3668, February 2004.
[BCP-78], S. Bradner, IETF Rights in Contributions, RFC3978, March
2005.
[RSVP] Braden et al., Resource ReSerVation Protocol (RSVP) -- Version
1 Functional Specification, RFC 2205, September 1997.
[INT-SERV] Braden, R., Clark, D. and (i).
Note thatS. Shenker, Integrated Services
in the detailsInternet Architecture: an Overview, RFC 1633, June 1994.
[GUARANTEED] Shenker et al., Specification of Guaranteed Quality of
Service, RFC2212
[CONTROLLED] Wroclawski, Specification of the signaling flow may vary slightly
depending on the actual approach usedControlled-Load Network
Element Service, RFC2211
[DIFFSERV] Blake et al., An Architecture for RSVP Proxy. For example, if
the [L-RSVP] approach was used insteadDifferentiated Services,
RFC 2475
[INT-DIFF] A Framework for Integrated Services Operation over
Diffserv Networks, RFC 2998, November 2000.
[RSVP-AGG] Baker et al, Aggregation of [RSVP-PROXY], an additional
PathRequest message would be needed from host to
Aggregator/Deaggregator/Proxy in orderRSVP for IPv4 and IPv6
Reservations, RFC 3175, September 2001.
[MPLS-TE] Awduche et al., "Requirements for Traffic Engineering over
MPLS", RFC 2702, September 1999.
[RSVP-TE] Awduche et al, RSVP-TE: Extensions to trigger the generation of
the Path messageRSVP for return direction.
But regardlessLSP Tunnels,
RFC 3209, December 2001.
[DSTE-PROTO] Le Faucheur et al, Protocol extensions for support of
Diff-Serv-aware MPLS Traffic Engineering, RFC 4124, June 2005.
[LSP-HIER] Kompella et al, Label Switched Paths (LSP) Hierarchy with
Generalized Multi-Protocol Label Switching (GMPLS) Traffic
Engineering (TE), RFC 4206, October 2005
[SEC-ARCH] Kent and Seo, Security Architecture for the detailsInternet
Protocol, RFC 4301, December 2005
12. Informative References
[DIFF-MPLS] Le Faucheur et al, MPLS Support of the call flow andDiff-Serv, RFC3270,
May 2002.
[DSTE-REQ] Le Faucheur et al, Requirements for support of the actualDiff-Serv-
aware MPLS Traffic Engineering, RFC3564, July 2003.
[6PE] De Clercq et al, Connecting IPv6 Islands over IPv4 MPLS using
IPv6 Provider Edge Routers (6PE), work in progress
[RSVP-IPSEC] Berger et al, RSVP
Proxy approach,Extensions for IPSEC Data Flows, RFC
2207
[RSVP-GEN-AGG] Le Faucheur et al, Generic Aggregate RSVP proxy may optionally be deployedReservations,
draft-ietf-tsvwg-rsvp-ipsec, work in combination
withprogress
[RSVP-TUN] Terzis et al., RSVP Aggregation over MPLS TEOperation Over IP Tunnels, RFC 2746,
January 2000
[RSVP-PREEMP] Herzog, Signaled Preemption Priority Policy Element,
RFC 3181
[L-RSVP] Manner et al., Localized RSVP, draft-manner-lrsvp-04.txt,
work in such a way which
ensures (when used on both the Host-Aggregator and Deaggregator-Host
sides, and when both end systems support RSVP) that:
(i) admission controlprogress.
[RSVP-PROXY] Gai et al., RSVP Proxy, draft-ietf-rsvp-proxy-03.txt
(expired), work in progress.
[RSVP-APPID] Bernet et al., Identity Representation for RSVP, RFC
3182.
[AUTOMESH] Vasseur and resource reservation is performed on
every segmentLeroux, Routing extensions for discovery of the end-to-end path (i.e. between source
hostMultiprotocol (MPLS) Label Switch Router (LSR) Traffic Engineering
(TE) mesh membership, draft-vasseur-ccamp-automesh-00.txt, work in
progress.
[SIP-RSVP] Camarillo, Integration of Resource Management and Aggregator, over the TE Tunnel betweenSession
Initiation Protocol (SIP), RFC 3312
13. Editor's Address:
Francois Le Faucheur
Cisco Systems, Inc.
Village d'Entreprise Green Side - Batiment T3
400, Avenue de Roumanille
06410 Biot Sophia-Antipolis
France
Email: flefauch@cisco.com
IPR Statements
The IETF takes no position regarding the
Aggregator and Deaggregator which itself has been subjectvalidity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to admission control by MPLS TE, between Deaggregator and
destination host)
(ii) this is achieved in both direction
(iii) RSVP signaling is localized between hosts and
Aggregator/Deaggregator, which may result in significant
reduction in reservation establishment delays (and in turn
in post dial delay in the case where these reservations
are pre-conditions for voice call establishment),
particularlyimplementation or use of the technology described in
this document or the case whereextent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the MPLS TE tunnels span
long distancesprocedures with high propagation delays.
9. Security Considerations
The security issues inherentrespect to the use of RSVP, RSVP Aggregation and
MPLS TE apply. Thoserights in RFC documents can be addressed as discussedfound in [RSVP], [RSVP-
AGG]BCP 78 and [RSVP-TE].
Section 7BCP 79.
Copies of [LSP-HIER] discusses security considerations stemming
from the fact thatIPR disclosures made to the implicit assumption of a binding between data
interfaceIETF Secretariat and the interface over which a control message is sent is
no longer valid. These security considerations are equally applicableany
assurances of licenses to be made available, or the present document.
In addition, in the case where the Aggregators dynamically resize the
TE tunnels based on the current levelresult of reservation, there are risks
that the TE tunnels usedan
attempt made to obtain a general license or permission for RSVP aggregation hog resources in the
core which could prevent other TE Tunnels from being established.
There are also potential risks that such resizing results in
significant computation and signaling as well as churn on tunnel
paths. Such risks can be mitigated by configuration options allowing
controluse of TE tunnel dynamic resizing (maximum Te tunnel size,
maximum resizing frequency,...) and/or possiblysuch proprietary rights by the useimplementers or users of TE
preemption.
Ifthis
specification can be obtained from the Aggregator and Deaggregator are also acting as IPsec Security
Gateways,IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard.
Please address the Security Considerationsinformation to the IETF at ietf-ipr@ietf.org.
Disclaimer of [SEC-ARCH] apply.
10. IANA Considerations
This document has no actions for IANA.
11. AcknowledgmentsValidity
This document builds on the [RSVP-AGG], [RSVP-TUN] and [LSP-HIER]
specifications. Also, we would like to thank Tom Phelan, John Drake,
Arthi Ayyangar, Fred Baker, Subha Dhesikan, Kwok-Ho Chan, Carol
Iturraldethe information contained herein are provided on an
"AS IS" basis and James Gibson for their input into this document.
12. Normative References
[RFC2119] S. Bradner, Key words for use in RFCs to Indicate
Requirement Levels, RFC2119, March 1997.
[RFC3668] S. Bradner, Intellectual Property Rights in IETF Technology,
RFC 3668, February 2004.
[BCP-78], S. Bradner, IETF Rights in Contributions, RFC3978, March
2005.
[RSVP] Braden et al., Resource ReSerVation Protocol (RSVP) -- Version
1 Functional Specification, RFC 2205, September 1997.
[INT-SERV] Braden, R., Clark, D.THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Notice
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and S. Shenker, Integrated Servicesrestrictions contained in BCP 78, and
except as set forth therein, the Internet Architecture: an Overview, RFC 1633, June 1994.
[GUARANTEED] Shenker et al., Specification of Guaranteed Quality of
Service, RFC2212
[CONTROLLED] Wroclawski, Specification of the Controlled-Load Network
Element Service, RFC2211
[DIFFSERV] Blake et al., An Architecture for Differentiated Services,
RFC 2475
[INT-DIFF]authors retain all their rights.
Appendix A Framework for Integrated Services Operation over
Diffserv Networks, RFC 2998, November 2000.
[RSVP-AGG] Baker et al, Aggregation- Optional Use of RSVP for IPv4 and IPv6
Reservations, RFC 3175, September 2001.
[MPLS-TE] Awduche et al., "Requirements for Traffic Engineering over
MPLS", RFC 2702, September 1999.
[RSVP-TE] Awduche et al, RSVP-TE: ExtensionsProxy on RSVP Aggregator
A number of approaches ([RSVP-PROXY], [L-RSVP]) have been, or are
being, discussed in the IETF in order to allow a network node to
behave as an RSVP for LSP Tunnels,
RFC 3209, December 2001.
[DSTE-PROTO] Le Faucheur et al, Protocol extensions for supportproxy which:
- originates the Resv Message (in response to the Path message) on
behalf of
Diff-Serv-aware MPLS Traffic Engineering, RFC 4124, June 2005.
[LSP-HIER] Kompella et al, Label Switched Paths (LSP) Hierarchy with
Generalized Multi-Protocol Label Switching (GMPLS) Traffic
Engineering (TE), RFC 4206, October 2005
[SEC-ARCH] Kent and Seo, Security Architecture for the Internet
Protocol, RFC 4301, December 2005
13. Informative References
[DIFF-MPLS] Le Faucheur et al, MPLS Supportdestination node
- originates the Path message (in response to some trigger) on
behalf of Diff-Serv, RFC3270,
May 2002.
[DSTE-REQ] Le Faucheur et al, Requirements for supportthe source node.
We observe that such approaches may optionally be used in conjunction
with the aggregation of Diff-Serv-
aware MPLS Traffic Engineering, RFC3564, July 2003.
[6PE] De Clercq et al, Connecting IPv6 IslandsRSVP reservations over IPv4 MPLS using
IPv6 Provider Edge Routers (6PE), workTE tunnels as
specified in progress
[RSVP-IPSEC] Berger et al,this document. In particular, we consider the case where
the RSVP Extensions for IPSEC Data Flows, RFC
2207
[RSVP-GEN-AGG] Le Faucheur et al, Generic AggregateAggregator/Deaggregator also behaves as the RSVP Reservations,
draft-ietf-tsvwg-rsvp-ipsec, workproxy.
The information is this Appendix is purely informational and
illustrative.
As discussed in progress
[RSVP-TUN] Terzis et al., RSVP Operation Over IP Tunnels, RFC 2746,
January 2000
[RSVP-PREEMP] Herzog, Signaled Preemption Priority Policy Element,
RFC 3181
[L-RSVP] Manner et al., Localized RSVP, draft-manner-lrsvp-04.txt,
work[RSVP-PROXY]:
"The proxy functionality does not imply merely generating a single
Resv message. Proxying the Resv involves installing state in progress.
[RSVP-PROXY] Gai et al.,the node
doing the proxy i.e. the proxying node should act as if it had
received a Resv from the true endpoint. This involves reserving
resources (if required), sending periodic refreshes of the Resv
message and tearing down the reservation if the Path is torn down."
Hence, when behaving as the RSVP Proxy, the RSVP Aggregator may
effectively perform resource reservation over the MPLS TE Tunnel (and
hence over the whole segment between the RSVP Aggregator and the RSVP
Deaggregator) even if the RSVP signaling only takes place upstream of
the MPLS TE Tunnel (i.e. between the host and the RSVP Proxy, draft-ietf-rsvp-proxy-03.txt
(expired), workaggregator).
Also, the RSVP Proxy can generate the Path message on behalf of the
remote source host in progress.
[RSVP-APPID] Bernet et al., Identity Representationorder to achieve reservation in the return
direction (i.e. from RSVP aggregator/Deaggregator to host).
The resulting Signaling Flow is illustrated below, covering
reservations for RSVP, RFC
3182.
[AUTOMESH] Vasseurboth directions:
I----I I--------------I I------I I--------------I I----I
I I I Aggregator/ I I MPLS I I Aggregator/ I I I
IHostI I Deaggregator/I I cloudI I Deaggregator/I IHostI
I I I RSVP Proxy I I I I RSVP Proxy I I I
I----I I--------------I I------I I--------------I I----I
==========TE Tunnel==========>
<========= TE Tunnel==========
Path Path
------------> (1)-\ /-(i) <----------
Resv I I Resv
<------------ (2)-/ \-(ii) ------------>
Path Path
<------------ (3) (iii) ------------>
Resv Resv
------------> <------------
(1)(i) : Aggregator/Deaggregator/Proxy receives Path message,
selects the TE tunnel, performs admission control over the TE Tunnel.
(1) and Leroux, Routing extensions for discovery of
Multiprotocol (MPLS) Label Switch Router (LSR) Traffic Engineering
(TE) mesh membership, draft-vasseur-ccamp-automesh-00.txt, work in
progress.
[SIP-RSVP] Camarillo, Integration(i) happens independently of Resource Management and Session
Initiation Protocol (SIP), RFC 3312
14. Editor's Address:
Francois Le Faucheur
Cisco Systems, Inc.
Village d'Entreprise Green Side - Batiment T3
400, Avenue de Roumanille
06410 Biot Sophia-Antipolis
France
Email: flefauch@cisco.com
IPR Statements
The IETF takes no position regardingeach other.
(2)(ii) : Aggregator/Deaggregator/Proxy generates the validity or scopeResv message
towards Host. (2) is triggered by (1) and (ii) is triggered by (i).
Before generating this Resv message, the Aggregator/Proxy performs
admission control of any
Intellectual Property Rights or other rightsthe corresponding reservation over the TE tunnel
that might be claimed to
pertain towill eventually carry the implementation or use ofcorresponding traffic.
(3)(iii) : Aggregator/Deaggregator/Proxy generates the technology describedPath message
towards Host for reservation in return direction. The actual trigger
for this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Informationdepends on the procedures with respect to rights in RFC documents canactual RSVP proxy solution. As an example,
(3) and (iii) may simply be
found in BCP 78triggered respectively by (1) and BCP 79.
Copies of IPR disclosures made to(i).
Note that the IETF Secretariat and any
assurancesdetails of licenses to be made available, or the result of an
attempt made to obtain a general license or permissionsignaling flow may vary slightly
depending on the actual approach used for RSVP Proxy. For example, if
the use of
such proprietary rights by implementers or users[L-RSVP] approach was used instead of this
specification can[RSVP-PROXY], an additional
PathRequest message would be obtainedneeded from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bringhost to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be requiredAggregator/Deaggregator/Proxy in order to implement
this standard.
Please addresstrigger the information togeneration of
the IETF at ietf-ipr@ietf.org.
DisclaimerPath message for return direction.
But regardless of Validity
This documentthe details of the call flow and of the information contained herein are providedactual RSVP
Proxy approach, RSVP proxy may optionally be deployed in combination
with RSVP Aggregation over MPLS TE Tunnels, in such a way which
ensures (when used on an
"AS IS" basisboth the Host-Aggregator and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Notice
Copyright (C) The Internet Society (2006). This documentDeaggregator-Host
sides, and when both end systems support RSVP) that:
(i) admission control and resource reservation is performed on
every segment of the end-to-end path (i.e. between source
host and Aggregator, over the TE Tunnel between the
Aggregator and Deaggregator which itself has been subject
to the rights, licensesadmission control by MPLS TE, between Deaggregator and restrictions containeddestination host)
(ii) this is achieved in BCP 78,both direction
(iii) RSVP signaling is localized between hosts and
except as set forth therein,Aggregator/Deaggregator, which may result in significant
reduction in reservation establishment delays (and in turn
in post dial delay in the authors retain all their rights.case where these reservations
are pre-conditions for voice call establishment),
particularly in the case where the MPLS TE tunnels span
long distances with high propagation delays.
Appendix AB - Example Usage of RSVP Aggregation over DSTE Tunnels for
VoIP Call Admission Control (CAC)
This Appendix presents an example scenario where the mechanisms
described in this document are used, in combination with other
mechanisms specified by the IETF, to achieve Call Admission Control
(CAC) of Voice over IP (VoIP) traffic over the packet core.
The information is that Appendix is purely informational and
illustrative.
Consider the scenario depicted in Figure A1. VoIP Gateways GW1 and
GW2 are both signaling and media gateways. They are connected to an
MPLS network via edge routers PE1 and PE2, respectively. In each
direction, a DSTE tunnel passes from the head-end edge router,
through core network P routers, to the tail-end edge router. GW1 and
GW2 are RSVP-enabled. The RSVP reservations established by GW1 and
GW2 are aggregated by PE1 and PE2 over the DS-TE tunnels. For
reservations going from GW1 to GW2, PE1 serves as the
aggregator/head-end and PE2 serves as the de-aggregator/tail-end. For
reservations going from GW2 to GW2, PE2 serves as the
aggregator/head-end and PE1 serves as the de-aggregator/tail-end.
To determine whether there is sufficient bandwidth in the MPLS core
to complete a connection, the originating and destination GWs each
send for each connection a Resource Reservation Protocol (RSVP)
bandwidth request to the network PE router to which it is connected.
The bandwidth request takes into account VoIP header compression,
where applicable.
As part of its Aggregator role, the PE router effectively performs
admission control of the bandwidth request generated by the GW onto
the resources of the corresponding DS-TE tunnel.
In this example, in addition to behaving as Aggregator/Deaggregator,
PE1 and PE2 behave as RSVP proxy. So when a PE receives a Path
message from a GW, it does not propagate the Path message any further.
Rather, the PE performs admission control of the bandwidth signaled
in the Path message over the DSTE tunnel towards the destination.
Assuming there is enough bandwidth available on that tunnel, the PE
adjusts its book-keeping of remaining available bandwidth on the
tunnel and generates a Resv message back towards the GW to confirm
resources have been reserved over the DSTE tunnel.
,-. ,-.
_.---' `---' `-+
,-'' +------------+ :
( | | `.
\ ,' CCA `. :
\ ,' | | `. ;
;' +------------+ `._
,'+ ; `.
,' -+ Application Layer' `.
SIP,' `---+ | ; `.SIP
,' `------+---' `.
,' `.
,' `.
,' ,-. ,-. `.
,' ,--+ `--+--'- --'\ `._
+-`--+_____+------+ { +----+ +----+ `. +------+_____+----+
|GW1 | RSVP| |______| P |___| P |______| | RSVP|GW2 |
| |-----| PE1 | { +----+ +----+ /+| PE2 |-----| |
| | | |==========================>| | | |
+-:--+ RTP | |<==========================| | RTP +-:--+
_|..__ +------+ { DSTE Tunnels ; +------+ __----|--.
_,' \-| ./ -'._ / |
| Access \ / +----+ \, |_ Access |
| Network | \_ | P | | / Network |
| / `| +----+ / | '
`--. ,.__,| | IP/MPLS Network / '---'- ----'
'`' '' ' .._,,'`.__ _/ '---' |
| '`''' |
C1 C2
Figure A1. Integration of SIP Resource Management, DSTE
and RSVP Aggregation
[SIP-RSVP] discusses how network quality of service can be made a
precondition for establishment of sessions initiated by the Session
Initiation Protocol (SIP). These preconditions require that the
participant reserve network resources before continuing with the
session. The reservation of network resources are performed through a
signaling protocol such as RSVP.
Our example environment relies of [SIP-RSVP] to synchronize RSVP
bandwidth reservations with SIP. For example, the RSVP bandwidth
requests may be integrated into the call setup flow as follows (See
call setup flow diagram in Figure A2):
- Caller C1 initiates a call by sending a SIP INVITE to VoIP
gateway GW1, which passes the INVITE along to the call control
agent (CCA). The INVITE message may contain a list of codecs
that the calling phone can support.
- VoIP gateway GW2, chooses a compatible codec from the list and
responds with a SIP message 183 Session Progress.
- When GW1 receives the SIP response message and learnswith the codec
to be used,SDP, it knowsdetermines how much bandwidth is required for the call.
- GW1 sends an RSVP Path message to PE1, requesting bandwidth for
the call.
- GW2 also sends an RSVP Path message to PE2.
- Assuming that the tunnel (from left to right) has sufficient
bandwidth, PE1 responds to GW1 with a Resv message
- Again assuming the tunnel (from right to left) has sufficient
bandwidth, PE2 responds to GW2 with a Resv message
- GW2 sends a SIP 200 OK message to GW1.
- GW1 sends a SIP UPDATE message to GW2.
- Upon receiving the UPDATE, GW2 sends the INVITE to the
destination phone, which responds with SIP message 180 RINGING.
- When (and if) the called party answers, the destination phone
responds with another SIP 200 OK which completes the connection
and tells the calling party that there is now reserved
bandwidth in both directions so that conversation can begin.
- RTP media streams in both directions pass through the DSTE
tunnels as they traverse the MPLS network.
IP-Phone/ IP-Phone/
TA-C1 GW1 PE1 CCA PE2 GW2 TA-C2
| INVITE|(SDP1) | INVITE | INVITE | | |
|---------->|-------|---------->|------------|------->| |
| 100|TRYING | | | | |
|<----------|-------|-----------| | | |
| 183|(SDP2) | | | | |
|<----------|-------|-----------|------------|--------| |
| | PATH | | | PATH | |
| |------>| | |<-------| |
| | RESV | | | RESV | |
| |<------| | |------->| |
| | | UPDATE|(SDP3) | | |
| |-------|-----------|------------|------->| |
| | | 200 OK|(SDP4) | | |
| |<------|-----------|------------|--------| INVITE |
| | | | | |---------->|
|180 RINGING| | 180|RINGING | |180 RINGING|
|<----------|<------|-----------|------------|--------|<----------|
| 200 OK | 200|OK | 200|OK | 200 OK |
|<----------|<------|-----------|<-----------|--------|<----------|
| | | | | | |
| | | DSTE|TUNNEL | | |
| RTP|MEDIA |-----------|------------| | |
|===========|=======|===========|============|========|==========>|
| | |-----------|------------| | |
| | | | | | |
| | |-----------|------------| | |
|<==========|=======|===========|============|========|===========|
| | |-----------|------------| | |
DSTE TUNNEL
Figure A2. VoIP QoS CAC using SIP with Preconditions
Through the collaboration between SIP resource management, RSVP
signaling, RSVP Aggregation and DS-TE as described above, we see
that:
a) the PE and GW collaborate to determine whether there is enough
bandwidth on the tunnel between the calling and called GWs to
accommodate the connection,
b) the corresponding accept/reject decision is communicated to the
GWs on a connection-by-connection basis, and
c) the PE can optimize network resources by dynamically adjusting
the bandwidth of each tunnel according to the load over that tunnel.
For example, if a tunnel is operating near capacity, the network may
dynamically adjust the tunnel size within a set of parameters.
We note that admission Control of voice calls over the core network
capacity is achieved in a hierarchical manner whereby:
- DSTE tunnels are subject to Admission Control over the
resources of the MPLS TE core
- Voice calls are subject to CAC over the DSTE tunnel bandwidth
This hierarchy is a key element in the scalability of this CAC
solution for voice calls over an MPLS Core.
It is also possible for the GWs to use aggregate RSVP reservations
themselves instead of per-call RSVP reservations. For example,
instead of setting one reservation for each call GW1 has in place
towards GW2, GW1 may establish one (or a small number of) aggregate
reservations as defined in [RSVP-AGG] which is used for all (or a
subset of all) the calls towards GW2. This effectively provides an
additional level of hierarchy whereby:
-
DSTE tunnels are subject to Admission Control over the
resources of the MPLS TE core
- Aggregate RSVP reservations (for the calls from one GW to
another GW) are subject to Admission Control over the DSTE
tunnels (as per the "RSVP Aggregation over TE Tunnels"
procedures defined in this document)
- Voice calls are subject to CAC by the GW over the aggregate
reservation towards the appropriate destination GW.
This pushes even further the scalability limits of this voice CAC
architecture.